32 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
Experiment XXIII. 
Iron. 
Specific gravity water 
at A C. = 1. 
Total percentage of 
increase of length 
= dl. 
Total percentage of 
decrease of specific 
gravity = dA. 
d\ 
dV 
7 '/849 
7-7771 
9-35 
•1002 
•0107 
7'7747 
12"65 
•1311 
•0104 
7-7730 
16-87 
•1529 
•0091 
7-7684 
20-73 
•2121 
•0091 
7-7520 
25"41* 
•4229 
•0167 
It will be observed that in all cases the ratio of the decrease of specific gravity to 
the increase of length at first increases to a maximum, then decreases, and again 
increases largely when the breaking strain has been reached. In any case, however, 
the alteration of density which can be produced by longitudinal traction is small, and 
in my own experiments never reached per cent., though several of the wires were 
strained to breaking 1 . 
Wertheim has also obtained similar results.! 
Relation eetween Moduli of Elasticity and Intermolecular Distance. 
If we denote the specific gravity of a substance by A, and A represent the atomic 
w r eight, the intermolecular distance will be proportional to UM =a. 
It is natural to suppose that as a diminishes the elasticity will increase, and in fact 
Wertheim has shown| that is the case, and moreover that approximately “ Young’s 
modulus ” varies inversely as a 7 . 
In the next table will be found the products of e X a 7 and r X a 7 for the annealed 
metals. 
Table IY. 
Metal. 
Specific gravity 
= A. 
Atomic weight 
A. 
Intermolecular 
distance 
=(£>*=- 
e x a 7 . 
r x a 7 . 
Iron (1) . 
7-759 
56-0 
1-932 
1994 xlO 8 
778 x10 8 
Platinum (1) .... 
21-300 
197-4 
2-100 
2688 x10 8 
1250 x10 s 
Copper (1) .... 
8-913 
63-5 
1-924 
1133xl0 8 
430 x10 8 
Zinc (1). 
7138 
65-0 
2-088 
1328 xlO 8 
586 x10 8 
Silver (1). 
10-491 
108-0 
2-175 
1712xl0 8 
627 xlO 8 
Aluminium (1) . 
2-732 
27-5 
2-159 
1473 x10 8 
580 x10 8 
Tin (1). 
7-264 
118-0 
2-533 
1852 x10 8 
812 x10 8 
Lead (1). 
11-193 
207-0 
2-644 
1510xl0 8 
669 x10 8 
* Wire broke. 
t Ann. de Cliimie, 1844, tom. xii. 
t Ibid. 
